1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, more specifically, a method for manufacturing a semiconductor device in which holes (cavities, pores or the like) are prevented from being generated in a crystalline semiconductor film.
2. Description of the Related Art
There is a method for manufacturing a semiconductor film including amorphous silicon having preferable properties by using an element which promotes crystallization as a method for forming a crystalline semiconductor film including silicon at low temperature and in short time. (See Reference 1: Japanese Patent Laid-Open No. H8-213316)
In this method, an amorphous silicon film is formed over a glass substrate, then a film including nickel is formed over the amorphous silicon film, and the amorphous silicon film is crystallized by heating. Accordingly, a crystalline silicon film is obtained.
Then, an amorphous silicon film is further formed through an oxide film that serves as an etching stopper over the crystalline silicon film, and heat treatment is again carried out. Accordingly, the nickel element is diffused into the amorphous silicon film from the crystalline silicon film, thereby decreasing the concentration of nickel in the crystalline silicon film.
The amorphous silicon film into which the nickel element is diffused is removed; however, an oxide film is formed over the surface by being heated during the crystallization. Therefore, the amorphous silicon film is removed after the oxide film is removed using hydrofluoric acid, and further, the oxide film serving as an etching stopper is removed. Accordingly, a crystalline silicon film having preferable properties can be obtained.
According to this method, a crystalline silicon film can be rapidly obtained at low temperature. Furthermore, concentration of nickel in the crystalline silicon film can be reduced.
The crystalline silicon film thus manufactured can be preferably used for a thin film transistor and a capacitor.